Coating compositions comprising perfluorocarbonsilane, such as perfluoroalkylalkyl silane, perfluoroalkylalkyl trichlorosilane can be used to treat a glass surface, such as the surface of a windshield of a vehicle or windows, to render it water repellent.
The perfluoroalkylalkylsilane or perfluoroalkylalkyltrichlorosilane based water repellents provide good water repellency on glass surfaces due to the high reactivity between the silane and the hydroxyl groups on the glass surface. However, they have limited durability and resistance to weathering and abrasion. They are also sensitive to trace amount of water during production and storage. Examples of perfluoroalkylalkyl silane or perfluoroalkylalkyl trichlorosilane based water repellents are disclosed in U.S. Pat. Nos. 5,523,162, and 5,523,161. To overcome the water sensitivity and to impart resistance to weathering and abrasion, additional components, such as hydrolysable silanes that are capable of hydrolysis to silica gel, are required in the perfluoroalkylalkylsilane or perfluoroalkylalkyltrichlorosilane based water repellents as described in the aforementioned U.S. Pat. No. 5,523,161. In addition, water drops on the surface treated with those silanes are not readily sliding off.
It is therefore still needed for a water repellent that is easy to produce and store, having good durability and improved water sliding property.